The Supreme Court heard a case last week that could add new limitations on class actions, potentially adding to a trend that has gained momentum within the judicial body in recent years.

The case pitted American Express against various merchants, which asked the Court to strike down a provision in their contracts with the credit card giant forbidding them from forming class actions. The contractual clause at the center of the dispute required the merchants to settle their disputes - in this case, antitrust claims - individually through arbitration.

The merchants argued that it was cost-prohibitive for them to file their claims individually. The hundreds of thousands of dollars necessary for hiring the experts needed to make the complex calculations typical in antitrust cases, they told the Court, only made sense on a collective level. While one merchant could not afford to bring an antitrust case, a group of them could do so, making it an ideal class action.

The oral arguments meandered from topic to topic as the justices showed little enthusiasm for the merchants' position.

Arguing on behalf of the merchants, Paul Clement, who appeared before the justices in the biggest case of last year involving the constitutionality of the Affordable Care Act, reminded the justices that a person didn't give up the rights granted to her under federal law by partaking in arbitration - a concept known as the vindication of rights doctrine.

None of the justices disagreed with the principle. They just wondered whether the facts in the case threatened these rights.

Clement's counterpart, Michael Kellogg, reiterated several times that the agreements with his client, American Express, did not forbid the claimants from pooling their resources in bringing individual cases, it only prevented them from bringing a class action.

Here too, the justices were unsure about the factual record established in the lower court proceedings. Did a confidentiality provision in the agreements prevent the merchants from sharing information and resources as Clement claimed? Or were they allowed to pool their resources in a limited but meaningful way as Kellogg argued? At one point, Chief Justice John Roberts asked, "how does that work again?"

Later in the proceeding, Justice Antonin Scalia mused over the exact question the Court was asked to answer in the appeal.

The oral argument came on the heels of the Court's recent decisions curbing class actions. In a 2011 decision, AT&T v. Concepcion, the Court allowed companies to evade class actions by directing their contractual partners into individual arbitration proceedings.

The ruling had an immediate impact. More than 75 class actions were stopped or significantly hampered within its first year, according to Public Citizen, a consumer advocacy organization. Plus, companies like Microsoftupdated their agreements with consumers in response to the decision. Concepcion will likely weigh heavily on the Court's thinking in the American Express case.

Besides the Concepcion case, the Court also ruled in favor of Wal-Mart in 2011, bringing to an end what was the largest employee class action in the nation's history. Both rulings have supplemented Congressional attempts to curb class actions during the past two decades.